Bottom loading control system with transient closing and liquid level controls



R. D. MARX 3,404,703 BOTTOM LOADING CONTROL SYSTEM WITH TRANSIENT Oct.8, 1968 CLOSING AND LIQUID LEVEL CONTROLS Filed July 2, 1964 3Sheets-Sheet l FIG. 1A.

MORGAN, FINNEGAN, DURHAM 8 PINE ATTORNEYS Oct. 8, 1968 R. D. MARX3,404,703

BOTTOM LOADING CONTROL SYSTEM WITH TRANSIENT CLOSING AND LIQUID LEVELCONTROLS Filed July 2, 1964 3 Sheets-Sheet 2 u N R I K i N r I i E '3 iINVENTOR. ROBERT D MARX MORGAN, FINNEGAN, DURHAM Bu PINE ATTORNEYS Oct.8, 1968 R. DOMARX BOTTOM LOADING CONTROL SYSTEM WITH TRANSIENT CLOSINGAND LIQUID LEVEL CONTROLS Filed July 2, 1964 IN VEN TOR.

ROBERT D. MARX 3 Sheets-Sheet 5 MORGAN, FlN NEGAN, DURHAM 8 PINEATTORNEYS United States Patent 3,404,703 BOTTOM LOADING CONTROL SYSTEMWITH TRANSIENT CLOSING AND LIQUID LEVEL 7 CONTROLS a Robert D. Marx,Valley Stream, N.Y.

.(952 Meeker Ave Brooklyn, N.Y. 11222) Continuation-impart ofapplication Ser. No. 117,675, v:Junev 16, 1 961. This application July2, 1964, Ser. No. 379,959 p 22 Claims. (Cl. 137-390) This inventionrelates to systems for the bottom loading of fluid storage vessels and,more particularly, to systems for the bottom loading of tanks such astruck tanks which transport liquid products. The systems may alsoprovide. bottom unloading but for convenience will be referred to asbottom loading systems.

.This application is a continuation-in-part of applicants priorcopending application Ser. No. 117,675, filed June 16, 1961, nowabandoned for Tank Bottom Transfer System.

It is known to employ bottom loading arrangements for truck tanks. Oneknown arrangement, sometimes referred to as a pressure bleed design,comprises a loading valve at the base of the tank which is biased by aspring into the closed position. The valve is housed within a cylinder.When a fluid source is connected to the valve outlet, the pressurethereof is in the direction which is against the face of the loadingvalve. This fluid ram pressure also communicates through suitablepassageways with the cylinder and would be directed against the rear ofthe loading valvctending to prevent its opening, were it not for a bleedline which relieves this back pressure and allows the forward pressureto predominate. The valve is accordingly forced open against the closingspring and the tank commences to fill.

, When the tank is filled, a float-actuated valve in the cylinder bleedline closes. Thus, both front and back faces of the balanced loadingvalve are subject to pressure from thefluid source. In this event, thedilferential force provided by the spring urges the valve closed.

Bottom loadingsystems have many advantages. Gan- -tries, superstructuresand swivel booms are not needed.

Only a single operator is required and he may stay safely on the ground.Being essentially a closed, automatic system, the bottom loadingtechnique avoids problems of contamination, pilfering and fume leakageand does not depend on operator 'accuracyfor a correct fill.

However, presently "employed bottom loading systems have a number ofsignificant disadvantages. Substantial pressurization of thefluidis'required to force the bottom valve open. In the course offorcing the valve open, the pressurized fluid undergoes excessive sprayand turbulence and if spring pressure is inadequate, the valve will onlypartially open. Static electric charges can build up to dangerouslevels, evaporation through the vents is aggravated and, unlesscarefully designed, the system may become unstable and oscillate as theturbulent fluid induces oscillation of the float valve. Loading ratesmay be reduced in forcing the valve open against the spring.Furthermore, float buoyancy is relied on to close the bleedline againstinput pump pressure. Therefore, the time at which the float valve closeswill vary depending on the particular value of pumping pressure. Sincethe time of closing is variable due to changes in this pressure, then'the liqiiid level will vary accordingly from its orig inal calibratedlevel which is set at some fixed pumping pressure. A limitation is thusplaced onfill accuracy. In

\the event of bleed line rupture or float valve malfunction, the loadingvalve will not close and tank rupture or overload spillage may occur.Many of the known systems 3,404,703 Patented Oct. 8, 1968 also requirean additional compartment valve for unloading.

In addition to the foregoing, many known and proposed systems arecharacterized by excessive pressure surges and shocks particularlyduring valve closing operations. Many of the systems have inherentaccuracy limitations due to alack of precise control over the movementof the loading/unloading valve. Accuracy limitations are also developeddue to inadequacies in the sensing and control means heretoforeemployed.

Additional limitations characterizing known and proposed systems relateto susceptibility to operator error and inadequate provisions foremergency shutdown.

It is, accordingly, an object of the invention to provide an improvedloading system for truck tanks and the like.

An additional object of the invention is to provide a bottom loadingsystem'for truck tanks and the like having improved loading accuracy andhigher loading rates.'

A still further object of the invention is to provide such a bottomloading system which has greater immunity from the eliects ofmalfunctions and manual errors in operating procedures.

A still further object of the invention is to provide a bottom loadingsystem for truck tanks and the like which has improved stability ofoperation.

An additional object of the invention is toprovide improved liquid levelcontrol means for truck tanks and the like.

A further object of the invention is to significantly reduce pressuresurges and shocks in the loading and unloading of truck tanks and astill further object of the invention is to provide more precise controlover the movement of the loading valve in such systems.

Other objects of the invention. include a bottom loading system whichfor a given product pressurization, permits maximum flow rate loading, asystem having features which facilitate emergency cut-01f of the loadingoperations, a system which eliminates excessive spray, turbulence,static and the like, and one in which the loading valve is also used forunloading operations.

These and other objects and advantages of the invention will be setforth in part hereinafter and in part will be obvious herefrom, or maybe learned by practice with the invention, the same being realized andattained by means of the instrumentalities and combinations pointed outin the appended claims.

The invention consists in the novel parts, constructions, arrangements,combinations and improvements herein shown and described.

Serving as illustrations of exemplary embodiments of the invention arethe drawings of which:

FIGURE 1 is an elevational view, partly in section and partly schematic,of a bottom loading system according to the invention;

FIGURE 1A is a detail view of a check valve employed in the system ofFIGURE 1;

FIGURE 2 isan elevational view partly in section and partly schematic ofanother bottom loading system embodiment;

FIGURE 3 is an elevational view partly in section and partly schematicof a return system particularly adapted for use in controlling theliquid level in truck tanks and the like; and

FIGURE 4 is an elevational and sectional detailed view of the returnvalve mechanism of FIGURE 3.

In the embodiment illustrated in FIGURES 1 and 1A, the bottom loadingsystem comprises a product flow valve 1 including a head seal 2 and astem 3 formed as the shank of a bolt 3a which also serves to secure-seal2 on the valve head 4. Valve 1 is adapted to control a product portdefined by a cage assembly 5 having a lower valve seat section 5athreadably or otherwise connected to a mounting ring 6 which is securedto the base B of a truck tank as by welding. Cage assembly 5 alsoincludes a pluarlity of circumferentially spaced struts 5b around whicha screen 7 is mounted. The struts are interconnected at their ends byseat section 5a and at their other ends by cage head 50. The latter alsoserves to define the base plate of a cylinder 8 which is a component ofa two-Way or double-acting actuator generally indicated at 9.

Valve 1 is operatively coupled to actuator 9, illustratively by meansincluding a clevis 10 and a lift rod 11 which is connected to stem 3 viathe clevis. Rod 11 passes axially through the cage assembly 5, plate 50and cylinder 8, its distal end passing through cover plate 12 andengaging resilient means comprising a spring 13 in a tubular housing 14.The latter connects to cover plate 12 via struts 15 which are secured asby bolting to the cover plate and to the wall of cylinder 8. Base plate5c is also secured to the cylinder wall. Seals, not shown, are providedin plates 50 and 12 where rod 11 passes therethrough.

Fast on rod 11 is piston 16 in the interior of cylinder 8. The pistondivides the cylinder int-o upper and lower chambers 8a and 8b,respectively, and is coupled to valve 1 via the rod 11. Both the pistonand the valve are resiliently urged downward by spring 13. As seen inthe figure, the effective working area of the piston is larger than thatof the product flow valve. For example, the

piston diameter may be 5 inches and the valve orifice diameter 4 /8inches.

The upper face of piston 16 is responsive to the fluid pressurization ofcylinder 8 derived from product pressure provided during the loadingoperation. Thus, the upper chamber 8a is connected to one end of a line19 "via a fitting 20 While the other end of the line is connectedvia afitting 21 to a coupling 22 threaded or otherwise connected to mountingring 6. The upper chamber 8a and upper face of piston 16 (which includesa pistoncylinder seal, not shown) will thus be responsive to pressureconditions in the product port controlled by valve 1. Coupling 22 isadapted for connection to a hose or other conduit which receives thetank product during bottom loading and discharges the same duringunloading as symbolized by the arrows F.

Lower chamber 8b and the lower face of piston 16 are pressurized from acontrolled fluid pressure system. As embodied, this pressure systemincludes a source of fluid pressure, e.g., the truck pneumatic supply25, a loading valve 26 and a discharge valve 27 (which may be combinedwith 26), each of which is connected to source and to a check valve 30.The fluid pressure system also includes liquid-level responsive means,illustratively a normally closed float valve 32 having an exhaustorifice 33, float 34, and inlet connector 35. Inlet 35 is connected toloading valve 26 and check valve 30.

The pressure system will generally also include additional remotecontrol valves, fusible pressure-relief means, interlock valves and thelike in accordance with specific installation requirements andcontrolling ordinances and regulations.

Typical operation of the system is as follows:

For bottom loading, valve 26 which is a normally closed spring-return,two-way valve is momentarily opened. During this interval, pneumaticpressure is transmitted from source 25 to chamber 8b of actuator 9 viacheck valve 30. With no product, or less than full capacity in the tank,float valve 32 is closed. The application of pressure to chamber 8bcauses an upward displacement of piston 16, which displacement istransmitted via rod 11 to valve 1 causing the latter to open against theaction of spring 13. As valve 1 is opened, the product commences toenter and fill the tank, passing between struts 5/2 and through screen7. It may be noted here that since valve 1 is opened independently ofproduct pumping pressure, ex-

cessive turbulence, spray, vapor loss and static, such as occurs in manyknown arrangements, are eliminated. Moreover, large pumping pressuresare not required as in the case where such pressures are required toforce the valve open against the spring. The inlet port may be of largediameter thereby facilitating the rapid loading of the product. i

When the product reaches a prescribed level, float 34 is fully displacedthereby opening float valve 32 and diverting pressure from chamber 8band the lower face of piston 16. With pressure so diverted, valve 1commences to close with the aid of spring 13. As the closed positionapproaches, there acts increasingly on the face of valve 1 the effectivepressure of the entering product tending to maintain valve 1 in its openposition. But, also acting on the valve is the piston 16, the upper faceof which is pressurized via chamber 8a in accordance with theproduct-developed pressure. Since piston 9 has an effective area largerthan the area of valve 1, then the force of piston 16 predominates andvalve 1 accordingly closes. This action is relatively smooth, preciseand automatic, and the closing rate varies in accordance with theproduct flow rate thus maintaining system calibration notwithstandingvariation in the flow rate.

In the event of certain malfunctions during the loading operation, forexample, a failure in the pressure system, a loss of pressure fromsource 25 or a break in the float valve lines, pressure will be divertedfrom chamber 8b and valve 1 will close as described above. Moreover, foremergency cutoff it is only necessary to relieve the pressure at chamber8b by any suitable means whereby valve I quickly closes. It may also beobserved that a bleed line is not necessary; line 19 can be as large asrequired, thus facilitating rapid control responses and a more accuratefill.

For unloading operations, valve 27 (three-way) is opened causing theapplication of pressure to chamber 8b. This occurs though float valve 32is opened because the latter is isolated by the action of check valve 30which closes the line to inlet 35 and diverts the pressure to chamber8b. Valve 1 accordingly opens as described hereinbefore. The tankproduct then passes out of the tank and into the receptacles, e.g.,airplane tanks, for receiving the product. When the tank compartment hasbeen emptied, valve 27 is closed, thus removing pressure from, andventing chamber 8b whereby valve 1 closes under the action of spring 13.

It may be seen from the above that the System of FIG- URE 1 providessafe, automatic, rapid and accurate product transfer with respect totruck tanks and the like.

The system of FIGURE 2 is also intended for use in connection with theloading and unloading of the compartments of a truck tank such as arefueler which carries aircraft fuel. As shown, the system includes acompartment valve preferably having a composition seat 111 adapted toseal the port 112, into and out of which the tank product passes.

Valve 110 is coupled, illustratively by direct connection of its stem113, to a pneumatic overbalanced actuator 115 conveniently provided witha piston 116 secured on stem 113 and located within a cylinder 117 so asto divide the cylinder into two compartments 117a, 117b, Chamber 117acommunicates with a control line 118 for purposes described hereinafterwhile chamber 117b is in communication with the face of valve 110 via abore 119 in stem 113. A spring 114 also acts on stem 113, urging valve110 towards its closed position.

Valve 10 is also coupled to controllable retard means embodied as adashpot 120 having a piston 121 conveniently connected to piston stem113. The dash pot cylinder 122 is mounted on the head of actuator 115and includes axially displaced orifices 123, 124 and a further outlet125 which communicates with a control line 126 for purposes describedhereinafter.

The system of FIGURE 2 includes a final liquid-level senser andassociated valve embodied as a float 130 which in the nonbuoyantposition maintains a normally closed needle valve 131 in the closedposition. Valve 131 communicates via line 126 with the outlet 125 ofdashpot 120.

.Float 130 is positioned to actuate (open) valve 131 when the tankproduct reaches the final desired level.

An adjustment flange 132 is provided on float 130 and has locking screws132a disposed in a slot 132b on a bracket 132c of tank 100 so that theposition of float 130 may be adjusted for adjustment of the finalproduct level.

The systern of FIGURE 2 also includes valve control means embodied as aprelevel senser and associated control valve comprising a prelevel float135 which may be adjusted in the same manner as float assembly 130 andwhich is adapted when buoyant to open a needle valve 136 to thereby ventthe line 118 communicating with chamber 117a of actuator 115. Line 118and chamber 117a are, in the closed position of valve 136, charged byoperation of a valve 139 which supplies pneumatic pressure thereto.Valve 139 is a valve having a spring-returned neutral, closed, positionsuch that release of the valve control after operation causes it toreturn to this neutral position to thus maintain line 118 and chamber117a in a charged condition provided there are no leaks. Operation ofthe valve 139 to its third position vents the charged system thusproviding means for rapid deactivation and closure of valve 110 shouldan emergency occur during loading or unloading.

For loading the compartment 100, a supply hose, not shown, fordelivering the product under pressure is connected to inlet 112. As inthe embodiment of FIGURES 1 and 1A, the product under pressure is notemployed to force valve 110 open and hence the usual shortcomings ofsuch conventional systems, including excessive spray, turbulence, staticcharges and the like, are thus avoided. Pump pressure cannot force thevalve 110 open because the pump force generated by way of bore 119 andthe upper face of piston 116 in actuator 115 is greater than the pumpforce acting directly against the face of valve 110.

Rather, valve 110 is opened independently of pump pressure by way of theactuator 115, control line 118, valve 139 and the source of pneumaticpressure which in a preferred form comprises the chassis brake airsystem 140.

Momentary actuation of valve 139 applies pneumatic pressure to chamber117a. Valve 110 responds by opening. Valve 139 may then be released and,provided there are no leaks, valve 110 remains opened. Product commencesto enter the compartment via port 112. Illustrative flow rates are inthe range 200 g.p.m. to 1000 g.p.m. When the liquid level reaches theprelevel point, float valve 135 releases the needle of valve 136 andthus vents the lines 118, 137 and chamber 117a.

Under the action of spring 114 which acts on stem 113, valve 110commences to close. In the course of closing, piston 121 of dashpot 120enters cylinder 122 thereof to thus provide a retardation actionassociated with the restricted outflow of product from orifices 123 and124 of the dashpot. A second and further retardation occurs when piston121 of dashpot 120 passes orifice 123.

Finally, upon reaching and sealing orifice 124 the closing actioninitiated by spring 114 is terminated since outlet 125 and line 126communicating therewith are closed. The system dimensions are designedsuch that this temporary termination of the closing action leaves valve110 partiallyopen, Hence the product continues to enter the system at areduced rate, e.g., 25 g.p.m.

When the final product level is reached, float 130 opens valve 131 tothereby open orifice 125 of the dashpot. Hence, valve 110 commencesagain to close under the action of spring 114 and also under the actionof the overbalanced actuator whose effectiveness increases as valve 110approaches the closed position. At this latter stage, pump pressureacting through bore 119 and chamber 11712 positively urges valve 110into its fully closed position. In this closing action, systemadjustments and dimensions are such as to prevent closing shock andclosing surges.

' It will be noted that the precise control over the action of valveduring its closing stages not only reduces undesirable shock and surgesbut also produces a more accurate fill. Closing shock pressure surges aslow as 15% at 1000 g.p.m., 10% at 500 g.p.m. and 3% at 250 g.p.m. arereadily realizable. Back pressure is similarly reduced.

Since the flow into the compartment is closely controlled by reducingthe valve opening and maintaining it in the interval between theprelevel and final level then accurate filling to a precisepredetermined level is more readily achieved even in the presence: ofvarying pumping pressures.

A liquid level control and liquid/vapor return system which is adaptedfor use in truck tank systems including those of FIGURES 1 and 2, isshown in FIGURES 3 and 4. The system includes a return system 200 havingan inlet 201 effectively at the desired liquid level.

Inlet 201 is controlled by valve 202 and an actuator 215, the lattercomprising (FIG. 4), piston 20 3. and cylinder 204, the cylinder beingcharged via cylinder inlet 205, lines 206, 207 and valve control 208from a source of pneumatic pressure 209 which may comprise the chassisair brake supply.

Piston 203 is connected to valve head 202 via stem 212. Cylinder 204 isconveniently mounted on brackets 235 upstanding from a flange member 236which is secured to inlet pipe section 241; the upper end of 241 definesthe inlet 201 and section 241 is in adjustable re lationship andcommunicates with the lower section 242 of the return system.Illustratively, this is effected by assembling sections 241 and 242 intelescoping relationships and providing appropriate sealing such aspacking 243. Liquid level may be controlled by appropriate positioningof section 241.

The outlet end of section 242 connects to the tank exterior and to areturn hose 250 through a shutoff valve 252. Return 250 may include asight glass 253, or a flow meter or the like for indicating flow through250.

The illustrated return system preferably has a capacity equal to inletflowthrough the loading valve. The latter may comprise a bottom loadingvalve 220 such as hereinbefore described, or top loading inlet 230.During loading operations, the control valve 208, which may beinterlocked with or a part of the loading valve control system viaconnection 260, 260, is actuated. whereby valve 202 opens to thus openinlet 201.

During loading, vapors are returned through 241 and 242; excessiveproduct is similarly returned when the level defined by inlet 201 isattained. Automatic or manual monitoring of flow in the line 250 marksthis latter condition and automatic or manual cut off of the loadingoperation is then effected. It may be seen that effective return actiontogether with accurate level control are achieved.

With loading concluded, valve 208 is manually operated, or automaticallycontrolled in response to flow in the return system, to deenergizeactuator 215. A spring 244 on stem 212 then causes valve 202 to closeinlet 201 to keep product from surging into the return system, e.g.,such as would occur during vehicle starting and stopping.

The invention in its broader aspects. is not limited to the specificmechanisms shown and described but departures may be made therefromwithin the scope of the accompanying claims without departing from theprinciples of the invention and without sacrificing its chiefadvantages.

What is claimed is:

1. A system for the bottom loading of a fluid product in a truck tankand the like comprising a normally closed bottom valve in said tankhaving a port for the admission of said product into said tank, adouble-acting fluid controlled actuator, longitudinally inextensiblemeans coupling said actuator to said valve in fixed space relation forcontrolling valve operation, fluid pressure means controllableindependently of product input pressure coupled to a first input of saidactuator for opening said valve and fluid pressure transmitting meansresponsive to product pressure in said port and coupled to a secondinput of said actuator to facilitate valve closure movement againstopposing product input pressure.

2. A system as set forth in claim 1 in which said controllable fluidpressure means includes product level responsive means for controllingthe pressurization of said first input of said actuator.

3. A system as set forth in claim 1 in which the working pressure areaof said actuator at said second input is larger than the effectivepressure area of said valve to provide a positive valve closing force inthe presence of product input pressure.

4. A system as set forth in claim 1 in which said controllable fluidpressure means comprises a pneumatic pressure source manually operated,valving means and product level responsive valving means interconnectedwith said pressure source for controlling the pressurization of saidactuator.

5. A system as set forth in claim 1 including retard means responsive tobottom valve position for controlling the closure rate of said valve.

6. A system as set forth in claim 5 including productlevel responsibemeans coupled to said valve closure retard means for controlling theretarding. action of said retard means.

7. A system for the bottom loading and discharge of a fluid productcarried in a truck tank or the like comprising a bottom valve in saidtank having a longitudinally inextensible stem and a port for saidloading and discharge, a double acting fluid controlled actuatorconnected in fixed space relation to said valve by said stem forcontrolling movement of said valve, resilient means coupled to saidvalve for urging closure thereof, means for selectively applyingpressure to a first input of said actuator for opening said valve and afluid connection between said port and a second input of said actuatorfor coupling product loading pressure to said actuator to facilitateclosure of said valve.

8. A system as set forth in claim 7 in which said actuator comprises acylinder and piston within said cylinder, said piston being mounted onsaid valve stem for movement therewith relative to said cylinder anddividing said cylinder into two opposing pressure chambers, one chamberbeing pressurized via said first input and the other chamber beingpressurized via said second input.

9. A system as set forth in claim 8 in which said piston has aneffective working area in said second input pressure chamber larger thanthe effective frontal area of said valve whereby said valve may beclosed regardless of the opposing product pressure thereagainst.

10. A system as set forth in claim 7 in which said means for selectivelyapplying pressure includes product level responsive pressure reliefmeans connected to said first input for initiating bottom valve closurewhen the liquid in said tank reaches a preselected level.

11. A system as set forth in claim 7 including retard means connected tosaid valve for regulating the closure rate thereof as a function ofvalve position and product level.

12. A system as set forth in claim 7 in which said means for selectivelyapplying pressure includes pneu matic loading means having momentarilyactuated valve means for providing said actuator with locked pressurewhereby a failure in said pressure means deenergizes said actuatorcausing said bottom valve to close.

13. A system as set forth in claim 7 including first prodnet levelresponsive pressure relief means operatively coupled to said first inputof said actuator for initiating bottom valve closure at a firstpreselected liquid level, retard means coupled to said bottom valveindependently of said first pressure relief means for regulating closurethereof as a function of valve position and second product levelresponsive pressure relief mean controlling said closure retard meansfor effecting final closure of said bottom valve at a second preselectedliquid level.

14. A system for the bottom loading of a fluid product in a truck tankand the like comprising a bottom valve in said tank for the controlledadmission of said product into said tank, and hydraulic transient valvecontrol means for controlling the closing action of said valveindependently of external pressurization including means for holdingsaid valve partially closed for a terminal period of the loadingoperation to reduce input flow rate as liquid approaches the desiredlevel whereby accurate level control is attained.

15. The system defined in claim 14 in which said transient control meanscomprises a dashpot having a controlled orifice and a float valvecontrolling said orifice.

16. The system defined in claim 14 in which said transient control meansis adapted to gradually reduce the closure rate of said bottom valvefollowing initial closure movement to thereby reduce shock and surges.

17. The system defined in claim 16 in which said transient control meanscomprises viscous damper means having a movable member connecteddirectly to said valve.

18. The system defined in claim 16 in which said transient control meansinclude means controlled according to product level for temporarilyholding said valve partially closed to facilitate accurate levelcontrol.

19. A system for the bottom loading of a fluid product in a truck tankand the like comprising a bottom valve in said tank, a fluid-operatedpiston actuator, connected directly to said bottom valve in fixed spacerelation therewith and actuator control means including a source ofpressure, control valve means and product-level respon sive pressurerelief means whereby said actuator may be pressurized from said sourceby said control valve means to open said bottom valve for producttransfer with said actuator being depressurized by said pressure reliefmeans when said product reaches a particular level.

20. The system as defined in claim 19 in which said control valve meansis operative to lock said actuator in a pressurized condition wherebypressure system failure will cause bottom valve closure.

21. The system as defined in claim 19 including valve closure controlmeans connected to said valve for temporarily stopping closure thereofand further product level responsive pressure relief means operativelycoupled to said closure control means for terminating said stoppingaction when a desired liquid level is attained.

22. The system as defined in claim 21 in which said closure controlmeans comprises a dash pot and said dash pot includes orifices forreducing closure rate to limit surges.

References Cited UNITED STATES PATENTS 2,707,378 5/1955 Ryan 251-62 X2,849,019 8/1958 Oliveau et al. 137--391 3,029,833 4/1962 De Frees137414 3,251,375 5/1966 Reed et al. 1374l4 WILLIAM F. ODEA, PrimaryExaminer.

DAVID R. MATTHEWS, Assistant Examiner.

1. A SYSTEM FOR THE BOTTOM LOADING OF A FLUID PRODUCT IN THE TRUCK TANKAND THE LIKE COMPRISING A NORMALLY CLOSED BOTTOM VALVE IN SAID TANKHAVING A PORT OF THE ADMISSION OF SAID PRODUCT INTO SAID TANK, ANDOUBLE-ACTING FLUID CONTROLLED ACUTATOR, LONGITUINALLY INEXTENSIBLEMEANS COUPLING SAID ACTUATOR TO SAID VALVE IN FIXED SPACED RELATION FORCONTROLLING VALVE OPERATION, FLUID PRESSURE MEANS CONTROLLABLEINDEPENDENTLY OF PRODUCT INPUT PRESSURE COUPLED TO A FIRST INPUT OF SAIDACTUATOR FOR OPENING SAID VALVE AND FLUID PRESSURE TRAMSMITTING MEANSRESPONSIVE TO PRODUCT PRESSURE IN SAID PORT AND COUPLED TO A SECONDINPUT OF SAID ACTUATOR TO FACILITATE VALVE CLOSURE MOVEMENT AGAINSTOPPOSING PRODUCT INPUT PRESSURE.